Field of the Invention
The present invention relates to an electrophotographic member for use in an electrophotographic apparatus, a process cartridge having the electrophotographic member, and an electrophotographic apparatus.
Description of the Related Art
In an electrophotographic apparatus (a copier, a facsimile, a printer, and the like using an electrophotographic system), an electrophotographic photosensitive member (hereinafter also referred to as “photosensitive member”) is charged with a charging roller and exposed with a laser beam or the like, so that an electrostatic latent image is formed on the photosensitive member. Subsequently, toner in a developing container is applied onto a developing roller with a toner supply roller and a toner regulating member. Using the toner transported to a development region with the developing roller, the electrostatic latent image on the photosensitive member is developed at the contact part or the proximity part between the photosensitive member and the developing roller. Subsequently, the toner on the photosensitive member is transferred to a recording paper with a transfer unit and fixed with heat and pressure. On the other hand, the toner remaining on the photosensitive member is removed with a cleaning blade.
In an electrophotographic apparatus, a conductive roller having an electro-conductive layer for use as developing roller or charging roller is required to have uniform and stable electric properties. Examples of the electro-conductive agent for use in imparting predetermined conductive properties to the electro-conductive layer include an ion conducting agent such as quaternary ammonium salt. The electro-conductive layer made conductive with the ion conducting agent has the ion conducting agent dispersed in a molecular level in the electro-conductive layer, so that the effects of the variation in the amount added and the process history on the electrical resistivity is smaller in comparison with an electro-conductive layer made from conductive particles such as carbon black. Consequently the electro-conductive layer has a uniform electrical resistance over the entire region, so that the developing roller enables uniform development of a developer on a photosensitive member and the charging roller enables uniform charging of the surface of a photosensitive member.
On the other hand, due to having migration properties, the ion conducting agent tends to migrate in the electro-conductive layer and exude from the surface. Due to the migration of the ion conducting agent in the electro-conductive layer, the electrical resistivity of a conductive roller changes over time in some cases. In addition, the ion conducting agent exuding from the surface adheres to the surface of a photosensitive member or the like in contact with the conductive roller, affecting the quality of an electrophotographic image in some cases.
Responding to the problem, in Japanese Patent Application Laid-Open No. 2011-118113, use of an ionic liquid having two hydroxyl groups allows the ionic liquid to be fixed to a urethane resin composition for preventing the ion conducting agent from exuding.
Further, in Japanese Patent Application Laid-Open No. H11-209633, a conductive material including a quaternary ammonium salt to which an ether structure is added is described as a conductivity imparting agent. According to the description, use of a quaternary ammonium salt having three hydroxyl groups, in particular, improves the durability under conduction of the conductive material. Herein, the durability under conduction means the small variation in electrical resistivity, when the conductive material is subjected to conduction for a long time.
According to the study by the present inventors, an electro-conductive layer including an ion conducting agent having two hydroxyl groups prevents the ion conducting agent from exuding from the electro-conductive layer due to fixation of the ion conducting agent to the electro-conductive layer. However, when the electro-conductive layer is left standing under a high temperature and high humidity environment for a long period, the photographic image is impaired due to residual deformation at the contact part with another member in some cases. Also, the electro-conductive layer including an ion conducting agent having three hydroxyl groups further prevents the ion conducting agent from exuding. Depending on the kind of anion of an ion conducting agent, however, when the electro-conductive layer is left standing under a high temperature and high humidity environment for a long period, the photographic image is impaired due to residual deformation at the contact part with another member in some cases.